Chapter 12
Eukaryotic Organisms
General Characteristics of Eukaryotic Organisms
• Five major groups
– Protozoa
– Fungi
– Algae
– Water molds
– Slime molds
• Include both human pathogens and organisms vital for human life
Protozoa
• Diverse group defined by three characteristics
– Eukaryotic
– Unicellular
– Lack a cell wall
• Motile by means of cilia, flagella, and/or pseudopodia (except subgroup, apicomplexans)
– Require moist environments
– Most live worldwide in ponds, streams, lakes, and oceans; critical members of
plankton
– Others live in moist soil, beach sand, and decaying organic matter
– Very few are pathogens
• Nutrition of Protozoa
– Most are chemoheterotrophic
– Obtain nutrients by phagocytizing bacteria, decaying organic matter, other
protozoa, or the tissues of host
– Few absorb nutrients from surrounding water
– Dinoflagellates and euglenoids are photoautrophic
• Reproduction in Protozoa
– Most reproduce asexually only (binary fission or schizogony)
– Few also have sexual reproduction
Protists
• Plasmodium causes malaria-look for ring form INSIDE RBC
• Trypanosoma-causes African Sleeping Sickness.. NO form inside RBC
• Entamoeba – cause amoebic dysentery—look for “fried egg”
Fungi
•
•
•
•
•
•
•
•
Chemoheterotrophic
Have cell walls typically composed of chitin
Lack chlorophyll; do not perform photosynthesis
Related to animals
The Significance of Fungi
– Decompose dead organisms and recycle their nutrients
– Form associations with roots of vascular plants, which help plants absorb water
and minerals
– Used for food, in religious ceremonies, and in manufacture of foods and
beverages
– Produce antibiotics
– Serve as important research tools
– 30% cause diseases of plants, animals, and humans
– Can spoil fruit, pickles, jams, and jellies
Nutrition of Fungi
– Acquire nutrients by absorption
– Most are saprobes
– Some trap and kill microscopic soil-dwelling nematodes
– Most are aerobic; some are anaerobic; many yeasts are facultative anaerobes
Reproduction in Fungi
– All have some means of asexual reproduction involving mitosis and cytokinesis
– Most also reproduce sexually
– Budding and asexual spore formation
Classification of Fungi
– Division based on sexual spores formed
– Division Zygomycota
• Rhizopus (black bread mold)
– Division Ascomycota (cup fungi)
• Penicillium (look like hand and fingers)
• Aspergillus (casuses aspergillosis)
• Peziza
• spores along cup—8 ascospores in an ascus—look like pease in a
pod
– Division Basidiomycota
• Coprinus (mushrooms)
• look for spores on gill slits
– Deuteromycetes
•
•
•
Heterogeneous collection of fungi whose sexual stages are unknown
rRNA analysis revealed that most deuteromycetes belong in the division
Ascomycota
Lichens
– Partnerships between fungi and photosynthetic microbes (green algae or
cyanobacteria)
– Abundant throughout the world, particularly in pristine habitats
– Grow on soil, rocks, leaves, tree bark, other lichens, and even on backs of
tortoises, in almost every habitat
– Occur in three basic shapes – fruticose, crusts, foliose
Parasitic Helminths and Vectors
• Parasitic worms have microscopic infective and diagnostic stages – usually eggs or larvae
• Arthropod vectors are animals that carry pathogens
– Mechanical vectors
– Biological vectors
• Disease vectors belong to two classes of arthropod
– Arachnida
– Insecta
• 2 basic phylum—Nematoda and Platyhelminthes
– Plathyhelminthes (flat worms)
• Taenia (tapeworm)—look for the 3-4 cross sections
• know scolex, proglottids and gravid proglottids
• Fasciola (sheep’s liver fluke)-looks like large leaf
• Clinorchis (Chinese liver fluke)-looks like Fasciola except MUCH smaller
– Nematodes (round worms)
• Enterobius (pinworm)
• Ascaris (look for mounts)
• Necator (new world hookworm)—look for hooks in mouth
• Trichinella (causes trichinosis)—look for spirals in muscle